The present invention has particular application in a heat transfer apparatus in which the heat transfer element, also called a sheet or plate, is heated by contact with a hot gaseous heat exchange fluid and is thereafter brought in contact with preferably a cool gaseous heat exchange fluid to which the heat transfer element gives up the heat that the heat transfer element has received by virtue of the heat transfer element's contact with the aforementioned hot gaseous heat exchange fluid.
One type of such heat exchange apparatus, which is commonly found in use, is that which those in the industry refer to as a rotary regenerative heat exchanger. Typically, such a rotary regenerative heat exchanger includes a cylindrical rotor that is divided into compartments and in each of which there are disposed a plurality of heat transfer plates which, as the aforementioned cylindrical rotor turns, are alternately exposed to a stream of a hot gaseous heat exchange fluid and then said cylindrical rotor is rotated whereupon the plurality of heat exchange plates become exposed to a stream of a cool gaseous heat exchange fluid that is to be heated. The compartments into which the cylindrical rotor of the heat exchanger is divided typically each house a plurality of heat transfer element basket assemblies that are suitably mounted therein and normally each embody a pie-shaped configuration. Each of the heat transfer element basket assemblies is designed to receive therein in supported relation thereto a plurality of heat transfer plates (e.g., sheets or elements). Each of these plurality of heat transfer plates when exposed to a hot gaseous heat exchange fluid absorbs heat therefrom, and then when each of these plurality of heat transfer plates is exposed to a cool gaseous heat exchange fluid, which is to be heated, transfers to the cool gaseous heat exchange fluid the heat that has been absorbed from the hot gaseous heat exchange fluid by each of the plurality of heat exchange plates.
Typically, such a prior art form of heat transfer element basket assembly comprises a pair of spaced end plates, which are held together by paired side straps that are designed to interconnect the end plates of the prior art form of heat transfer element basket assembly along the sides of the prior art form of heat transfer element basket assembly, such as, in the manner described and shown in U.S. Pat. Nos. 3,314,472 and 4,606,400. In accordance with the prior art teachings of U.S. Pat. Nos. 3,314,472 and 4,606,400 a plurality of heat transfer plates are stacked in closely spaced relationship within the housing of the prior art form of heat transfer element basket assembly in order to thereby provide a plurality of passageways between adjacent ones of the heat transfer plates such that heat exchange fluids may pass therethrough. Furthermore, in accordance with such prior art teachings, side straps are made to interconnect the spaced end plates of the prior art form of heat transfer element basket assembly in such a manner so as to extend in pairs along the opposite sides of the stacked array of heat exchange elements. With further regard to such prior art teachings, on each side of the heat exchange element there is provided a first side strap, which extends between the upper regions of the spaced end plates of the prior art form of heat transfer element basket assembly and a second side strap, which extends between the lower region of the spaced end plates of the prior art form of heat transfer element basket assembly in spaced, parallel relationship to the aforementioned first side strap. These side straps may be flanged inwardly along the longitudinal edge lying at the edge of the prior art form of heat transfer element basket assembly so as to thereby provide a retaining surface that is designed to be operative for purposes of preventing the heat transfer plates from falling out of the open ends of the prior art form of heat transfer element basket assembly, as shown, by way of exemplification, in U.S. Pat. No. 3,314,472. Typically, in accordance with prior art teachings one or more such retaining bars are welded between the end plates of the prior art form of heat transfer element basket assembly across the top and bottom ends thereof so as to thereby further assist in keeping the heat transfer element plates from falling out of the open ends of such a prior art form of heat transfer element basket assembly.
Although such prior art forms of heat transfer element basket assemblies are still commonly found in use, such prior art forms of heat transfer element basket assemblies are typically subject to rotational torsion of the side straps that are utilized therein as well as to lateral deformation due to the bowing of such side straps, which are employed therein to interconnect the spaced end plates thereof. U.S. Pat. No. 4,739,822 to Mergler, which is entitled “Low Profile Element Basket Assembly For Heat Exchanger,” and which is assigned to the same assignee as the present invention, and which is incorporated herein in its entirety, is directed to an invention that is designed to address such rotational torsion and lateral deformation from which such prior art forms of heat transfer element basket assemblies have been found to suffer. While the invention to which U.S. Pat. No. 4,739,822 is directed has been found to be able to attain its stated goals, improvements to the heat transfer element basket assembly, which is described and illustrated in U.S. Pat. No. 4,739,822 are deemed to be still possible to be made.
Illustrated in FIGS. 1 and 2 of the present patent application is the heat transfer element basket assembly 130 of U.S. Pat. No. 4,739,822. This heat transfer element basket assembly 130 is comprised of a plurality of heat transfer element plates 132, which are arranged in a stacked array so as to thereby provide a plurality of flow passages located between adjacent ones of the heat transfer element plates 132. This stacked array of heat transfer element plates 132 is suitably arranged so as to be disposed between a first end plate 134 located at one end of the heat transfer element basket assembly 130 and a second end plate 136 located at the other end of the heat transfer element basket assembly 130. These end plates 134 and 136 are suitably positioned so as to abut the ends of the stacked array of heat transfer element plates 132 and are held in position there by means of side straps 140, 142 and 150, 152. These side straps 140, 142 and 150, 152 are disposed along opposite sides of the stacked array of heat transfer element plates 132 so as to thereby be positioned at the upper and lower edges, respectively, of the heat transfer element plates 132, whereby the side straps 140, 142 and 150, 152 are operative to effect an interconnection of the t first end plate 134 with the second end plate 136, the first end plate 134 and the second end plate 136 being spaced apart from one another.
Continuing with the description of the heat transfer element basket assembly 130 of U.S. Pat. No. 4,739,822, the side plates 140 and 142, as described and illustrated in U.S. Pat. No. 4,739,822 are each welded at one end to the upper right corner and to the upper left corner, respectively, of the end plate 134 and in addition are also each welded at their other end to the upper right corner and to the upper left corner, respectively, of the end plate 136, which is located at the opposite end of the heat transfer element basket assembly from where the end plate 134 is located. In a similar manner, the side plates 150 and 152, as described and illustrated in U.S. Pat. No. 4,739,822, are each welded at one end to the lower right corner and to the lower left corner, respectively, of the end plate 134 and in addition are also each welded at their other end to the lower right corner and to the lower left corner, respectively, of the end plate 136, which is located at the opposite end of the heat transfer element basket assembly from where the end plate 134 is located.
With further reference thereto, the side straps 140, 142, 150 and 152 of the heat transfer element basket assembly 130 are, as described and illustrated in U.S. Pat. No. 4,739,822, flanged along their respective longitudinal edges that extend in juxtaposed relation to the upper and lower edges, respectively, of the heat transfer element basket assembly 130. To this end, the side straps 140 and 142 are provided with the flanges 141 and 143, respectively. These flanges 141 and 143 extend inwardly from the inside longitudinal edges of the side straps 140 and 142, respectively, so as to be located adjacent to the upper edges of the heat transfer element plates 132. In a similar manner, the side straps 150 and 152 are provided with the flanges 151 and 153, respectively. These flanges 151 and 153 extend inwardly from the inside longitudinal edges of the side straps 150 and 152, respectively, so as to be located adjacent to the lower edges of the heat transfer element plates 132. These upper flanges 141 and 143 and these lower flanges 151 and 153 function to provide retaining surfaces along the upper and lower edges of the heat transfer element basket assembly 130, which are designed to be operative to prevent the heat transfer element plates 132, which are stacked within the heat transfer element basket assembly from falling out of the open ends of the heat transfer element basket assembly 130 during the transportation thereof, or the handling thereof, or the installation thereof. In addition to these upper flanges 141 and 143 and these lower flanges 151 and 153, retaining bars 138 are typically also tack-welded between the end plates 134 and 136 at the open top and bottom of the heat transfer element basket assembly 130 intermediate the side straps 140, 142 and 150, 152 in order to thereby further assist in preventing the heat transfer element plates 132, which are stacked within the heat transfer element basket assembly 130, from falling out of the open ends of the heat transfer element basket assembly 130.
In accordance with the invention to which U.S. Pat. No. 4,739,822 is directed, a stiffening member 160 is disposed intermediate, that is, preferably midway between and parallel to the spaced end plates 134 and 136 of the heat transfer element basket assembly 130. This stiffening member 160 is suitably positioned therewithin so as to extend transversely across the heat transfer element basket assembly 130. Furthermore, this stiffening member 160, as described and illustrated in U.S. Pat. No. 4,739,822, is welded at the lateral edges thereof to the side straps 140, 142, 150 and 152 to which reference has been had hereinbefore in order to thereby structurally interconnect the side straps 140, 142 and 150, 152 at a point that is near the mid-span of heat transfer element basket assembly 130 so as to thereby increase the structural integrity of the frame of the element basket assembly 130.
With further reference to the stiffening member 160, as best understood with reference to FIG. 2a of the present patent application, the stiffening member 160 may comprise a single plate 175, which is similar in nature to the end plates 132 and 134 previously described herein, which extend from the top to the bottom and from side to side across the entire cross-sectional area of the heat transfer element basket assembly 130 at the respective opposite ends thereof. Continuing with the description thereof, the single stiffening member 175, in accordance with the teachings of U.S. Pat. No. 4,739,822, is welded at each of the lateral edges thereof to each of the upper side straps 140 and 142 and lower side straps 150 and 152 as best understood with FIG. 2 of the drawings in order to thereby structurally interconnect all of the side straps 140, 142, 150 and 152 with one another.
Alternatively, as best understood with reference to FIG. 2b of the present patent application, the stiffening member 160 may comprise a pair of spaced elongated plank-like dual members 170a and 170b, which are suitably positioned so as to extend across the upper region of the heat transfer element basket assembly 130 and across the lower region of the heat transfer element basket assembly 130, respectively. With further reference thereto, the member 170a is welded at the lateral edges thereof to the upper side straps 140 and 142, whereas the member 170b is welded at the lateral edges thereof to the lower side straps 150 and 152.
Continuing herein with the description thereof, both the single stiffing member 175 and the dual stiffening members 170a and 170b are designed to be operative to provide a cross-link that is suitable for interconnecting the upper side straps 140 and 142 with one another and that is also suitable for interconnecting the lower side straps 150 and 152 with one another, at or near the mid-span of the heat transfer element basket assembly 130 between the spaced end plates 132 and 134 of the heat transfer element basket assembly 130 in order to thereby increase the structural integrity of the frame of the heat transfer element basket assembly 130. As a consequence thereof, not only is the weight capacity of the heat transfer element basket assembly 130 increased, but also in addition the rotational torsion of the side straps 140, 142 and 150, 152 as well as the lateral deformation of the frame of the heat transfer element basket assembly 130 are also effectively prevented. Although not shown in FIG. 2a of the present patent application, the single stiffening member 175 is capable in addition of being utilized as a means of effecting therewith the lifting of the heat transfer element basket assembly 130.
The heat transfer element basket assembly 130 as described and illustrated in U.S. Pat. No. 4,739,822 has been found to require an extensive amount of time to fabricate due to the amount of hand welding required thereby. To this end, the use of four separate side straps 140, 142, 150, and 152 and two separate end plates 134 and 136 requires that the heat transfer element basket assembly 130 be completely welded by hand during fabrication. Further to this point, such hand welding during fabrication requires not only that there be extra time allotted for purposes of effecting the fit up of the welding fixtures that are needed to accomplish the hand welding, but in addition extra personnel are also required for this purpose, which in turn not only is expensive, but also introduces the possibility of there being quality assurance issues associated therewith. It has been found that such extra time can cause delays in the assembly line process, which is employed for purposes of effecting therewith the fabrication of the heat transfer element basket assembly 130. Accordingly, a need has been found to exist for a heat transfer element basket assembly that for purposes of the fabrication thereof can be assembled without hand welding being required.
Additionally, an excessive amount of material is used in fabricating the single stiffening member 160, dual stiffening member 170a and 170b, and end plates 134 and 136 of the heat transfer element basket assembly 130, which is described and illustrated in U.S. Pat. No. 4,739,822. Furthermore, the size and shape of the stiffening member 160, 170a, and 170b and end plates 134 and 136 that are employed in the heat transfer element basket assembly 130, which is described and illustrated in U.S. Pat. No. 4,739,822, require that they be welded during the fabrication process. As such, this results in scrap material being produced as well as in adding cost to the fabrication of the heat transfer element basket assembly 130. Accordingly, a need has also been found to exist for a heat transfer element basket assembly that does not result in excessive material being required for the fabrication thereof.
Another disadvantage that is associated with the heat transfer element basket assembly 130, which is described and illustrated in U.S. Pat. No. 4,739,822, is that the flanges 141, 143, 151, and 153 on the side straps 140, 142, 150, and 152 have been found to be operative to prevent the flow of fluid from reaching the heat transfer element plates 132. Accordingly, in addition a need has also been found to exist for a heat transfer element basket assembly in which less of the flow of fluid would be blocked by the structural members of the heat transfer element basket assembly.